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Unlike in C++03, a constant-expression is not an unevaluated operand in C++11. 

Split out a new ExpressionEvaluationContext flag for this case, and don't treat
it as unevaluated in C++11. This fixes some crash-on-invalids where we would
allow references to class members in potentially-evaluated constant expressions
in static member functions, and also fixes half of PR10177.

The fix to PR10177 exposed a case where template instantiation failed to provide
a source location for a diagnostic, so TreeTransform has been tweaked to supply
source locations when transforming a type. The source location is still not very
good, but MarkDeclarationsReferencedInType would need to operate on a TypeLoc to
improve it further.

Also fix MarkDeclarationReferenced in C++98 mode to trigger instantiation for
static data members of class templates which are used in constant expressions.
This fixes a link-time problem, but we still incorrectly treat the member as
non-constant. The rest of the fix for that issue is blocked on PCH support for
early-instantiated static data members, which will be added in a subsequent
patch.

llvm-svn: 146955
This commit is contained in:
Richard Smith 2011-12-20 02:08:33 +00:00
parent 50660440a1
commit 764d2fe666
11 changed files with 133 additions and 46 deletions
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13
clang/include/clang/Sema/Sema.h
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@ -512,12 +512,17 @@ public:
/// evaluated at run-time, if at all.
enum ExpressionEvaluationContext {
/// \brief The current expression and its subexpressions occur within an
/// unevaluated operand (C++0x [expr]p8), such as a constant expression
/// or the subexpression of \c sizeof, where the type or the value of the
/// expression may be significant but no code will be generated to evaluate
/// the value of the expression at run time.
/// unevaluated operand (C++11 [expr]p7), such as the subexpression of
/// \c sizeof, where the type of the expression may be significant but
/// no code will be generated to evaluate the value of the expression at
/// run time.
Unevaluated,
/// \brief The current expression and its subexpressions occur within a
/// constant expression. Such a context is not potentially-evaluated in
/// C++98, but is potentially-evaluated in C++11.
ConstantEvaluated,
/// \brief The current expression is potentially evaluated at run time,
/// which means that code may be generated to evaluate the value of the
/// expression at run time.

15
clang/lib/Parse/ParseExpr.cpp
View File

@ -247,11 +247,12 @@ Parser::ParseAssignmentExprWithObjCMessageExprStart(SourceLocation LBracLoc,
ExprResult Parser::ParseConstantExpression() {
// C++ [basic.def.odr]p2:
// C++03 [basic.def.odr]p2:
// An expression is potentially evaluated unless it appears where an
// integral constant expression is required (see 5.19) [...].
// C++98 and C++11 have no such rule, but this is only a defect in C++98.
EnterExpressionEvaluationContext Unevaluated(Actions,
Sema::Unevaluated);
Sema::ConstantEvaluated);
ExprResult LHS(ParseCastExpression(false));
return ParseRHSOfBinaryExpression(LHS, prec::Conditional);
@ -1041,7 +1042,7 @@ ExprResult Parser::ParseCastExpression(bool isUnaryExpression,
if (T.expectAndConsume(diag::err_expected_lparen_after, "noexcept"))
return ExprError();
// C++ [expr.unary.noexcept]p1:
// C++11 [expr.unary.noexcept]p1:
// The noexcept operator determines whether the evaluation of its operand,
// which is an unevaluated operand, can throw an exception.
EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated);
@ -1439,8 +1440,8 @@ Parser::ParseExprAfterUnaryExprOrTypeTrait(const Token &OpTok,
// [...] The operand is either an expression, which is an unevaluated
// operand (Clause 5) [...]
//
// The GNU typeof and alignof extensions also behave as unevaluated
// operands.
// The GNU typeof and GNU/C++11 alignof extensions also behave as
// unevaluated operands.
EnterExpressionEvaluationContext Unevaluated(Actions,
Sema::Unevaluated);
Operand = ParseCastExpression(true/*isUnaryExpression*/);
@ -1456,8 +1457,8 @@ Parser::ParseExprAfterUnaryExprOrTypeTrait(const Token &OpTok,
// [...] The operand is either an expression, which is an unevaluated
// operand (Clause 5) [...]
//
// The GNU typeof and alignof extensions also behave as unevaluated
// operands.
// The GNU typeof and GNU/C++11 alignof extensions also behave as
// unevaluated operands.
EnterExpressionEvaluationContext Unevaluated(Actions,
Sema::Unevaluated);
Operand = ParseParenExpression(ExprType, true/*stopIfCastExpr*/,

3
clang/lib/Sema/SemaDeclCXX.cpp
View File

@ -10515,7 +10515,8 @@ void Sema::MarkVTableUsed(SourceLocation Loc, CXXRecordDecl *Class,
// not have a vtable.
if (!Class->isDynamicClass() || Class->isDependentContext() ||
CurContext->isDependentContext() ||
ExprEvalContexts.back().Context == Unevaluated)
ExprEvalContexts.back().Context == Unevaluated ||
ExprEvalContexts.back().Context == ConstantEvaluated)
return;
// Try to insert this class into the map.

19
clang/lib/Sema/SemaExpr.cpp
View File

@ -1199,7 +1199,8 @@ diagnoseUncapturableValueReference(Sema &S, SourceLocation loc,
VarDecl *var, DeclContext *DC) {
switch (S.ExprEvalContexts.back().Context) {
case Sema::Unevaluated:
// The argument will never be evaluated, so don't complain.
case Sema::ConstantEvaluated:
// The argument will never be evaluated at runtime, so don't complain.
return CR_NoCapture;
case Sema::PotentiallyEvaluated:
@ -9330,7 +9331,7 @@ void Sema::PopExpressionEvaluationContext() {
// temporaries that we may have created as part of the evaluation of
// the expression in that context: they aren't relevant because they
// will never be constructed.
if (Rec.Context == Unevaluated) {
if (Rec.Context == Unevaluated || Rec.Context == ConstantEvaluated) {
ExprCleanupObjects.erase(ExprCleanupObjects.begin() + Rec.NumCleanupObjects,
ExprCleanupObjects.end());
ExprNeedsCleanups = Rec.ParentNeedsCleanups;
@ -9392,6 +9393,16 @@ void Sema::MarkDeclarationReferenced(SourceLocation Loc, Decl *D) {
// We are in an expression that is not potentially evaluated; do nothing.
return;
case ConstantEvaluated:
// We are in an expression that will be evaluated during translation; in
// C++11, we need to define any functions which are used in case they're
// constexpr, whereas in C++98, we only need to define static data members
// of class templates.
if (!getLangOptions().CPlusPlus ||
(!getLangOptions().CPlusPlus0x && !isa<VarDecl>(D)))
return;
break;
case PotentiallyEvaluated:
// We are in a potentially-evaluated expression, so this declaration is
// "used"; handle this below.
@ -9663,6 +9674,10 @@ bool Sema::DiagRuntimeBehavior(SourceLocation Loc, const Stmt *Statement,
// The argument will never be evaluated, so don't complain.
break;
case ConstantEvaluated:
// Relevant diagnostics should be produced by constant evaluation.
break;
case PotentiallyEvaluated:
case PotentiallyEvaluatedIfUsed:
if (Statement && getCurFunctionOrMethodDecl()) {

2
clang/lib/Sema/SemaExprMember.cpp
View File

@ -140,7 +140,7 @@ static IMAKind ClassifyImplicitMemberAccess(Sema &SemaRef,
return IMA_Mixed_StaticContext;
if (SemaRef.getLangOptions().CPlusPlus0x && hasField) {
// C++0x [expr.prim.general]p10:
// C++11 [expr.prim.general]p12:
// An id-expression that denotes a non-static data member or non-static
// member function of a class can only be used:
// (...)

32
clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
View File

@ -66,17 +66,16 @@ void Sema::InstantiateAttrs(const MultiLevelTemplateArgumentList &TemplateArgs,
// FIXME: This should be generalized to more than just the AlignedAttr.
if (const AlignedAttr *Aligned = dyn_cast<AlignedAttr>(TmplAttr)) {
if (Aligned->isAlignmentDependent()) {
// The alignment expression is not potentially evaluated.
EnterExpressionEvaluationContext Unevaluated(*this,
Sema::Unevaluated);
if (Aligned->isAlignmentExpr()) {
// The alignment expression is a constant expression.
EnterExpressionEvaluationContext Unevaluated(*this,
Sema::ConstantEvaluated);
ExprResult Result = SubstExpr(Aligned->getAlignmentExpr(),
TemplateArgs);
if (!Result.isInvalid())
AddAlignedAttr(Aligned->getLocation(), New, Result.takeAs<Expr>());
}
else {
} else {
TypeSourceInfo *Result = SubstType(Aligned->getAlignmentType(),
TemplateArgs,
Aligned->getLocation(),
@ -380,7 +379,7 @@ Decl *TemplateDeclInstantiator::VisitVarDecl(VarDecl *D) {
// We already have an initializer in the class.
} else if (D->getInit()) {
if (Var->isStaticDataMember() && !D->isOutOfLine())
SemaRef.PushExpressionEvaluationContext(Sema::Unevaluated);
SemaRef.PushExpressionEvaluationContext(Sema::ConstantEvaluated);
else
SemaRef.PushExpressionEvaluationContext(Sema::PotentiallyEvaluated);
@ -462,8 +461,9 @@ Decl *TemplateDeclInstantiator::VisitFieldDecl(FieldDecl *D) {
if (Invalid)
BitWidth = 0;
else if (BitWidth) {
// The bit-width expression is not potentially evaluated.
EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated);
// The bit-width expression is a constant expression.
EnterExpressionEvaluationContext Unevaluated(SemaRef,
Sema::ConstantEvaluated);
ExprResult InstantiatedBitWidth
= SemaRef.SubstExpr(BitWidth, TemplateArgs);
@ -591,8 +591,9 @@ Decl *TemplateDeclInstantiator::VisitFriendDecl(FriendDecl *D) {
Decl *TemplateDeclInstantiator::VisitStaticAssertDecl(StaticAssertDecl *D) {
Expr *AssertExpr = D->getAssertExpr();
// The expression in a static assertion is not potentially evaluated.
EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated);
// The expression in a static assertion is a constant expression.
EnterExpressionEvaluationContext Unevaluated(SemaRef,
Sema::ConstantEvaluated);
ExprResult InstantiatedAssertExpr
= SemaRef.SubstExpr(AssertExpr, TemplateArgs);
@ -653,9 +654,9 @@ Decl *TemplateDeclInstantiator::VisitEnumDecl(EnumDecl *D) {
// The specified value for the enumerator.
ExprResult Value = SemaRef.Owned((Expr *)0);
if (Expr *UninstValue = EC->getInitExpr()) {
// The enumerator's value expression is not potentially evaluated.
// The enumerator's value expression is a constant expression.
EnterExpressionEvaluationContext Unevaluated(SemaRef,
Sema::Unevaluated);
Sema::ConstantEvaluated);
Value = SemaRef.SubstExpr(UninstValue, TemplateArgs);
}
@ -2321,11 +2322,12 @@ TemplateDeclInstantiator::InitFunctionInstantiation(FunctionDecl *New,
}
Expr *NoexceptExpr = 0;
if (Expr *OldNoexceptExpr = Proto->getNoexceptExpr()) {
EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated);
EnterExpressionEvaluationContext Unevaluated(SemaRef,
Sema::ConstantEvaluated);
ExprResult E = SemaRef.SubstExpr(OldNoexceptExpr, TemplateArgs);
if (E.isUsable())
E = SemaRef.CheckBooleanCondition(E.get(), E.get()->getLocStart());
if (E.isUsable()) {
SourceLocation ErrLoc;
llvm::APSInt NoexceptVal;

3
clang/lib/Sema/SemaType.cpp
View File

@ -1055,7 +1055,8 @@ static QualType inferARCLifetimeForPointee(Sema &S, QualType type,
// If we are in an unevaluated context, like sizeof, assume ExplicitNone and
// don't give error.
} else if (S.ExprEvalContexts.back().Context == Sema::Unevaluated) {
} else if (S.ExprEvalContexts.back().Context == Sema::Unevaluated ||
S.ExprEvalContexts.back().Context == Sema::ConstantEvaluated) {
implicitLifetime = Qualifiers::OCL_ExplicitNone;
// If that failed, give an error and recover using __autoreleasing.

28
clang/lib/Sema/TreeTransform.h
View File

@ -2898,7 +2898,7 @@ bool TreeTransform<Derived>::TransformTemplateArgument(
Expr *SourceExpr = Input.getSourceDeclExpression();
if (SourceExpr) {
EnterExpressionEvaluationContext Unevaluated(getSema(),
Sema::Unevaluated);
Sema::ConstantEvaluated);
ExprResult E = getDerived().TransformExpr(SourceExpr);
SourceExpr = (E.isInvalid() ? 0 : E.take());
}
@ -2932,9 +2932,9 @@ bool TreeTransform<Derived>::TransformTemplateArgument(
llvm_unreachable("Caller should expand pack expansions");
case TemplateArgument::Expression: {
// Template argument expressions are not potentially evaluated.
// Template argument expressions are constant expressions.
EnterExpressionEvaluationContext Unevaluated(getSema(),
Sema::Unevaluated);
Sema::ConstantEvaluated);
Expr *InputExpr = Input.getSourceExpression();
if (!InputExpr) InputExpr = Input.getArgument().getAsExpr();
@ -3182,6 +3182,9 @@ QualType TreeTransform<Derived>::TransformType(QualType T) {
template<typename Derived>
TypeSourceInfo *TreeTransform<Derived>::TransformType(TypeSourceInfo *DI) {
// Refine the base location to the type's location.
TemporaryBase Rebase(*this, DI->getTypeLoc().getBeginLoc(),
getDerived().getBaseEntity());
if (getDerived().AlreadyTransformed(DI->getType()))
return DI;
@ -3595,7 +3598,8 @@ TreeTransform<Derived>::TransformConstantArrayType(TypeLocBuilder &TLB,
Expr *Size = TL.getSizeExpr();
if (Size) {
EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated);
EnterExpressionEvaluationContext Unevaluated(SemaRef,
Sema::ConstantEvaluated);
Size = getDerived().TransformExpr(Size).template takeAs<Expr>();
}
NewTL.setSizeExpr(Size);
@ -3640,9 +3644,6 @@ TreeTransform<Derived>::TransformVariableArrayType(TypeLocBuilder &TLB,
if (ElementType.isNull())
return QualType();
// Array bounds are not potentially evaluated contexts
EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated);
ExprResult SizeResult
= getDerived().TransformExpr(T->getSizeExpr());
if (SizeResult.isInvalid())
@ -3680,8 +3681,9 @@ TreeTransform<Derived>::TransformDependentSizedArrayType(TypeLocBuilder &TLB,
if (ElementType.isNull())
return QualType();
// Array bounds are not potentially evaluated contexts
EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated);
// Array bounds are constant expressions.
EnterExpressionEvaluationContext Unevaluated(SemaRef,
Sema::ConstantEvaluated);
// Prefer the expression from the TypeLoc; the other may have been uniqued.
Expr *origSize = TL.getSizeExpr();
@ -3728,8 +3730,9 @@ QualType TreeTransform<Derived>::TransformDependentSizedExtVectorType(
if (ElementType.isNull())
return QualType();
// Vector sizes are not potentially evaluated contexts
EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated);
// Vector sizes are constant expressions.
EnterExpressionEvaluationContext Unevaluated(SemaRef,
Sema::ConstantEvaluated);
ExprResult Size = getDerived().TransformExpr(T->getSizeExpr());
if (Size.isInvalid())
@ -6913,9 +6916,6 @@ TreeTransform<Derived>::TransformCXXUuidofExpr(CXXUuidofExpr *E) {
E->getLocEnd());
}
// We don't know whether the expression is potentially evaluated until
// after we perform semantic analysis, so the expression is potentially
// potentially evaluated.
EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated);
ExprResult SubExpr = getDerived().TransformExpr(E->getExprOperand());

9
clang/test/CXX/expr/expr.prim/expr.prim.general/p12-0x.cpp
View File

@ -10,3 +10,12 @@ struct S {
int i = sizeof(S::m); // ok
int j = sizeof(S::m + 42); // ok
struct T {
int n;
static void f() {
int a[n]; // expected-error {{invalid use of member 'n' in static member function}}
int b[sizeof n]; // ok
}
};

15
clang/test/CodeGenCXX/vla.cpp
View File

@ -1,5 +1,19 @@
// RUN: %clang_cc1 -triple x86_64-apple-darwin %s -emit-llvm -o - | FileCheck %s
template<typename T>
struct S {
static int n;
};
template<typename T> int S<T>::n = 5;
int f() {
// Make sure that the reference here is enough to trigger the instantiation of
// the static data member.
// CHECK: @_ZN1SIiE1nE = weak_odr global i32 5
int a[S<int>::n];
return sizeof a;
}
// rdar://problem/9506377
void test0(void *array, int n) {
// CHECK: define void @_Z5test0Pvi(
@ -40,4 +54,3 @@ void test0(void *array, int n) {
// CHECK-NEXT: ret void
}

40
clang/test/SemaCXX/PR10177.cpp Normal file
View File

@ -0,0 +1,40 @@
// RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s
template<typename T, typename U, U> using alias_ref = T;
template<typename T, typename U, U> void func_ref() {}
template<typename T, typename U, U> struct class_ref {};
template<int N>
struct U {
static int a;
};
template<int N> struct S; // expected-note 2{{here}}
template<int N>
int U<N>::a = S<N>::kError; // expected-error 2{{undefined}}
template<typename T>
void f() {
// FIXME: The standard suggests that U<0>::a is odr-used by this expression,
// but it's not entirely clear that's the right behaviour.
(void)alias_ref<int, int&, U<0>::a>();
(void)func_ref<int, int&, U<1>::a>(); // expected-note {{here}}
(void)class_ref<int, int&, U<2>::a>(); // expected-note {{here}}
};
int main() {
f<int>(); // expected-note 2{{here}}
}
namespace N {
template<typename T> struct S { static int n; };
template<typename T> int S<T>::n = 5;
void g(int*);
template<typename T> int f() {
int k[S<T>::n];
g(k);
return k[3];
}
int j = f<int>();
}